1. Field of the Invention
The present invention relates to a door checker for an automobile, and particularly to an improvement in a door checker for an automobile, comprising: a case secured to one of a body of an automobile and a door pivotally supported on the body for turning movement; a check plate which movably extends through the case to be connected to the other of the body and the door and which is provided in its opposite sides with ball guide grooves extending in a lengthwise direction; a pair of ball holders accommodated in the case and capable of advancing and retracting toward and away from the opposite sides of the check plate; a pair of balls which are retained in hemispherical ball housings formed in the ball holders and which are rollably engaged in the ball guide grooves; and a check spring for biasing the ball holders toward the check plate.
2. Description of the Related Art
A conventional door checker for an automobile is disclosed, for example, in Japanese Utility Model Publication No. 58-20059.
In the conventional door checker for an automobile, the application of a grease to the ball and the ball housing is effective to smooth the rotation of the balls in the ball housings and the rolling of the balls in the ball guide grooves. However, the present inventors found the following disadvantages: if the door checker is used over a long term, dust deposited in each of the ball guide grooves may enter a space between the ball and the ball housing with the rolling of the ball, and the entering dust hinders the rotation of the ball within the ball housing to stick the ball. The ball rubs the ball guide groove without being rolled within the ball guide groove, causing not only an increased resistance to the opening and closing of the door but also an uncomfortable friction noise.
The present invention has been accomplished with such circumstance in view, and it is an object of the present invention to provide a door checker for an automobile, wherein the sticking of the balls due to the entering dust can be prevented, and a smooth rotation and rolling of the balls can be ensured over a long term.
To achieve the above object, according to a first feature of the present invention, there is provided a door checker for an automobile, comprising: a case secured to one of a body of an automobile and a door pivotally supported on said body for turning movement; a check plate which movably extends through said case to be connected to the other of said body and said door and which is provided in its opposite sides with ball guide grooves extending in a lengthwise direction; a pair of ball holders accommodated in said case and capable of advancing and retracting toward and away from the opposite sides of said check plate; a pair of balls which are retained in hemispherical ball housings formed in said ball holders and which are rollably engaged in said ball guide grooves; and a check spring for biasing said ball holders toward said check plate, wherein a recess for retaining a grease on an inner surface of each of said ball housings and for accommodating a dust therein is formed in the inner surface of each of said ball housings.
With the first feature, when the ball is rolled in the ball guide groove while being rotated in the ball housing due to the opening and closing of the door, the surface of the ball is lubricated by the grease retained in the recess in the ball housing, thereby smoothly carrying out the rotation of the ball in the ball housing and the rolling of the ball in the ball guide groove. If a dust deposited to the ball guide groove enters a space between the surface of the ball and the inner surface of the ball housing accompanied by the rotation of the ball, the dust is pushed out and accommodated into the nearby recess by a surface pressure between the ball and a landing portion and a cleaning effect provided by the grease. Consequently, it is possible to prevent a disadvantage that the dust remains adhering to the surface of the ball to stick the ball. Therefore, the smooth rotation and rolling of the ball can be ensured over a long term, and the generation of a friction noise due to the rubbing of the ball guide groove by the ball can be prevented.
According to a second feature of the present invention, in addition to the first feature, the recess has at least portions extending in the lengthwise direction of the ball guide groove through the center of the inner surface of the ball housing.
With the second feature, the lubrication of the ball by the grease and the accommodation of the dust in the recess can be effectively carried out by the rolling of the ball in the ball guide groove in the lengthwise direction.
According to a third feature of the present invention, in addition to the first or second feature, the recess is formed so that its outer end is closed by contact portions between the ball and an inner peripheral surface of the ball housing.
With the third feature, the entrance of the dust into the recess can be minimized by the contact portions between the ball and the inner peripheral surface of the ball housing.